// Copyright (C) 1999-2001 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved.  Use of this class is limited.
// Please see the LICENSE for more information.

package com.oreilly.servlet.multipart;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * A <code>MacBinaryDecoderOutput</code> filters MacBinary files to normal files
 * on the fly; optimized for speed more than readability.
 * 
 * @author Jason Hunter
 */
public class MacBinaryDecoderOutputStream extends FilterOutputStream {
    private int bytesFiltered = 0;
    private int dataForkLength = 0;

    public MacBinaryDecoderOutputStream(OutputStream out) {
        super(out);
    }

    @Override
    public void write(byte b[]) throws IOException {
        write(b, 0, b.length);
    }

    @Override
    public void write(byte b[], int off, int len) throws IOException {
        // If the write is for content past the end of the data fork, ignore
        if (bytesFiltered >= (128 + dataForkLength)) {
            bytesFiltered += len;
        }
        // If the write is entirely within the data fork, write it directly
        else if (bytesFiltered >= 128 && (bytesFiltered + len) <= (128 + dataForkLength)) {
            out.write(b, off, len);
            bytesFiltered += len;
        }
        // Otherwise, do the write a byte at a time to get the logic above
        else {
            for (int i = 0; i < len; i++) {
                write(b[off + i]);
            }
        }
    }

    @Override
    public void write(int b) throws IOException {
        // Bytes 83 through 86 are a long representing the data fork length
        // Check <= 86 first to short circuit early in the common case
        if (bytesFiltered <= 86 && bytesFiltered >= 83) {
            int leftShift = (86 - bytesFiltered) * 8;
            dataForkLength = dataForkLength | (b & 0xff) << leftShift;
        }

        // Bytes 128 up to (128 + dataForkLength - 1) are the data fork
        else if (bytesFiltered < (128 + dataForkLength) && bytesFiltered >= 128) {
            out.write(b);
        }

        bytesFiltered++;
    }
}
